CoCrMo alloys are one of the most commonly used materials for hip arthroplasty, knee and dental because of its mechanical properties, corrosion resistance, wear resistance and biocompatibility. In this study, CoCrMo alloys consisting of 1.68 to 4.33%Pd are produced by investment casting process under argon atmosphere. The microstructures and mechanical properties of CoCrMo alloy were studied using X-ray diffraction, optical microscopy, scanning electron microscopy, Knoop indentation hardness tests, focusing on the influences on the different palladium additives. The measured microhardness values of CoCrMo alloys having different palladium ratio are seen to be load-dependent. The observed load dependence was rationalized using the Hays-Kendall model and it was found that the resultant load-independent hardness decreases with increase of palladium ratios. As a results, microhardness decreases with increase of palladium amount.
CoCrMo alloys are often used as the material for metal artificial joint because of their high corrosion resistance and mechanical properties. In this study CoCrMo alloys having different palladium amount of produced by investment casting method. Scanning electron microscopy, X-ray diffraction method and indentation tests were used to examine the mechanical properties of the alloys. Indentation experiments were carried out using Vickers indenter that the loads range from 0.245 to 9.8 N. The alloys exhibit significant load-dependence (i.e., indentation size effect). Meyer's law, proportional specimen resistance model, and Hays-Kendall model were used to analyze the load dependence of the hardness. As a results for load-independent determination of the CoCrMo alloys, the Hays-Kendall model is found to be more effective than the proportional specimen resistance model and microhardness values decreases with increase of the Pd content.
The alumina-zirconia composites are one of the relatively good and promising candidates for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. The aim of the present work is to analyze the mechanical properties of these composites, where zirconia content was varied from 5 to 50 wt%. The citrate gel method, similar to the polymerized complex method, was used to synthesize these ceramics. Scanning electron microscopy, X-ray diffraction and microhardness tests are used to characterize synthesized materials. The examined material exhibits the behaviour of indentation size effect. Modified proportional resistance model are used to analyze the load dependence of the microhardness. X-ray diffraction analysis was used to calculation of the grain size and dislocation density. It is found that hardness is decreased when the zirconia content increases with enlargement of grain size.
The citrate gel method, similar to the polymerized complex method, was used to synthesize homogeneous tetragonal zirconia at 1000°C. Nanocrystalline tetragonal phase has been fully stabilized at wide temperature range with 10 mol.% CaO, MgO, and Y_2O_3 addition. Scanning electron microscopy, X-ray diffraction, and microhardness tests are used to characterize synthesized materials. The grain size and dislocation density were calculated from X-ray diffraction data. The examined material exhibits indentation size effect behavior. Results revealed that the Vickers and Knoop microhardness are dependent on indentation test load. Geometrically necessary dislocation model and modified proportional resistance model are used to analyze the load dependence of the microhardness. The highest hardness values were obtained for the samples with CaO addition; however the lowest values were acquired for sample stabilized with Y_2O_3 by using both Knoop and Vickers techniques. This situation might be explained using the Hall-Petch relation.
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